Whether a solar battery is worth it depends on two important factors...
How much energy from your solar panel installation is available to be stored rather than exported.
How much of that stored energy could you use.
(Real-world comparison below)
To answer the question, ask yourself the following questions…
How much energy can I generate?
How much excess energy would be available to store in the solar battery?
How much electricity do I use?
What time of day do I use a lot of energy?
The more energy a battery can store each day, the more likely it is that a solar battery is worthwhile. Consuming as much of your solar generation as possible should be the main objective when installing solar panels.
The more energy that you can use the better the payback period. You will be able to increase your self-consumption by a greater degree. Especially if you have higher usage in the morning and evenings.